With a thread brake thread is squeezed between a fixed roller with a relatively hard surface and a moveable roller that can be moved horizontally and has a rubber elastic surface. Pressure of the movable roller against the fixed roller and the resultant deformation of the rubber elastic roller surface permits the thread tension to be adjusted to the desired value. Thereby, the roller with the hard surface generally also serves to deflect the thread from the bobbin creel in the direction of a lapping frame with a wrap angle of approx. 90.degree.. Such a known thread brake is shown and described in U.S. Pat. No. 4,535,956 which is assigned to the assignee of the present invention.
With the known thread brakes, problems may occur particularly in the case of a thread breakage. However, the existing thread guards ascertain that the lapping process is immediately interrupted in case of a thread breakage whereby, in some cases, the pressure force between the rollers is simultaneously increased so that the thread brake stops the advancement of the thread practically simultaneously with the lapping machine. This makes it possible to largely prevent after-running or stretching of the still intact threads. However, at the particular thread brake where the thread breakage occurred, it is not possible to prevent a certain length of thread from passing between the rollers before the thread is stopped, since there is a delay of several fractions of a second between the detection of the thread break at the thread guard and the triggering of the machine stoppage. Due to inertia, the rollers continue to turn during this interval, so that a thread length of up to 10 meters or more is pulled off the bobbin and transported through the thread brake.
Without tractive force, this thread, which is no longer under control, then leaves the thread brake on a straight line and falls onto the thread field below, where it may cause entanglements and additional thread breaks. Thus, the restart of the installation will require a labor-intensive and time-consuming unraveling of the threads which may cause relatively long down times.
Consequently, it is the purpose of the invention to create a method and apparatus for the breaking of thread, with the aid of which free advancement of a torn thread will be prevented in case of a thread break.